This invention relates to a system in which pulse sources to a counter are switched without changing the value in the counter; and more particularly to a system in which the output of one or more counters determines some parameter used for control of a function such as movement of a motor shaft or the amount of power supplied to a device. The pulse sources may be one with manual control and one with microprocessor control, with feedback.
Systems for numerical controlled machining of parts have been controlled by digital pulse systems which include up-down counters and various types of processors. The present invention relates to a system for control of motors and R.F. power for automatic zoning of high-grade silicon. The ability to automate requires (a) accurate and precise measurements of speed and position, (b) the ability to easily and accurately process this data and compare to a preset program for crystal growth, and (c) the ability to go from manual to automatic control without disturbing the crystal growth process. Analysis of these requirements showed that digital signal processing was superior to analog. A bonus feature of digital processing is to allow for future flexibility of the system with reasonable costs.
United States patents of interest include U.S. Pat. No. 3,488,478 to Gilbert which discloses apparatus in which computer signals are fed to a comparator, the output signal from the comparator being fed to a NOR gate to which a clock pulse source is also connected. The outputs of gates and of a flip-flop outputs are routed to a logic patchboard and then to a digital computer.
U.S. Pat. No. 3,916,327 to Lampen et al discloses a circuit in which a digital clock or ascillator has an output connected to one input of a gate. Output of a voltage comparator is connected to one of the inputs of each of a pair of gates. The outputs of the latter gates are applied to an up-cown counter. Outputs of the up-down counter are connected to a D/A converter. The output of the D/A converter is connected to inputs of voltage comparators and also provides an output for the device. Diodes provide a display from the counter.
U.S. Pat. No. 3,990,327 to Hakozaki discloses circuitry wherein an up-down counter is controlled by a gate which is enabled by closure of a manual switch and a variable pulse generator. The up-down counte is also controlled by a gate which is enabled by a computer.
U.S. Pat. No. 4,241,418 to Stanley shows use of a microprocessor to produce signals to select clock cycle periods.
U.S. Pat. No. 4,496,936 to Kramer shows digital shaft encoders and digital-analog conversion for the shaft encoders.